Fix admin interface issues and 404 errors

- Create adminEvents.js router to handle /api/admin/events endpoints
- Mount events router in admin.js to fix 404 errors
- Fix admin layout CSS - changed from static to flex layout
- Update AdminSidebar positioning from static to relative
- Add missing PUT endpoints for general and security settings
- Fix frontend environment variables in docker-compose.local.yml
- Add build args to Dockerfile.dev for environment variables
- Update CORS to accept requests from all dev servers
- Remove unused imports from SettingsPage

This fixes:
- Events page 404 error
- Admin layout misalignment (sidebar and content on different rows)
- Settings page not loading
- CORS issues between frontend and backend

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/src/routes/adminSettings.js

@@ -227,6 +227,80 @@ router.put('/theme', adminAuth, async (req, res) => {
   }
 });
 
+// Update general settings
+router.put('/general', adminAuth, async (req, res) => {
+  try {
+    const settings = req.body;
+
+    // Update or insert each setting
+    for (const [key, value] of Object.entries(settings)) {
+      await db('app_settings')
+        .insert({
+          setting_key: key,
+          setting_value: JSON.stringify(value),
+          setting_type: 'general',
+          updated_at: new Date()
+        })
+        .onConflict('setting_key')
+        .merge({
+          setting_value: JSON.stringify(value),
+          updated_at: new Date()
+        });
+    }
+
+    // Log activity
+    await db('activity_logs').insert({
+      activity_type: 'general_settings_updated',
+      actor_type: 'admin',
+      actor_id: req.user.id,
+      actor_name: req.user.username,
+      metadata: JSON.stringify({ settings_count: Object.keys(settings).length })
+    });
+
+    res.json({ message: 'General settings updated successfully' });
+  } catch (error) {
+    console.error('General settings update error:', error);
+    res.status(500).json({ error: 'Failed to update general settings' });
+  }
+});
+
+// Update security settings
+router.put('/security', adminAuth, async (req, res) => {
+  try {
+    const settings = req.body;
+
+    // Update or insert each setting
+    for (const [key, value] of Object.entries(settings)) {
+      await db('app_settings')
+        .insert({
+          setting_key: key,
+          setting_value: JSON.stringify(value),
+          setting_type: 'security',
+          updated_at: new Date()
+        })
+        .onConflict('setting_key')
+        .merge({
+          setting_value: JSON.stringify(value),
+          updated_at: new Date()
+        });
+    }
+
+    // Log activity
+    await db('activity_logs').insert({
+      activity_type: 'security_settings_updated',
+      actor_type: 'admin',
+      actor_id: req.user.id,
+      actor_name: req.user.username,
+      metadata: JSON.stringify({ settings_count: Object.keys(settings).length })
+    });
+
+    res.json({ message: 'Security settings updated successfully' });
+  } catch (error) {
+    console.error('Security settings update error:', error);
+    res.status(500).json({ error: 'Failed to update security settings' });
+  }
+});
+
 // Get storage info
 router.get('/storage/info', adminAuth, async (req, res) => {
   try {